Phosphatidylinositol-specific phospholipases C (PI-PLCs) are important enzymes participating in transmembrane signal transduction. The structures of the two major species of these enzymes: bacterial Ca2+-nondependent enzyme from B. cereus and mammalian Ca2+-dependent PLCδ1 from rat brain in the complexes with the polar head groups of their substrates have been previously solved. Although these structures show few differences as compared to free enzymes, there is a compelling evidence that full catalytic activity of PI-PLC necessitates interaction of the enzyme with the entire substrate, including the hydrophobic fatty acid chains. In this work we develop new tightly binding and cleavage-resistant analogs of phosphatidylinositol, using relatively minor modifications of the structure. Two synthesized analogs, 2-amino-2-deoxy-PI (8) and the conformationally constrained analog (10) had binding affinities (Ki) in 10 μM range. 15N-1H HSQC NMR spectra of uniformly 15N-labeled bacterial Ca2+-nondependent and Ca2+-dependent phospholipases C, btPLC and saPLC1, respectively, displayed changes upon ligand binding that suggest an occurrence of a conformational change.
磷脂酰肌醇特异性
磷脂酶 C(
PI-PLCs)是参与跨膜
信号转导的重要酶。这些酶的两个主要种类:来自 B. cereus 的不依赖 Ca2+ 的细菌酶和来自大鼠大脑的依赖 Ca2+ 的哺乳动物 PLCδ1 与其底物极性头基的复合物的结构以前已经解决。虽然这些结构与游离酶相比几乎没有什么不同,但有令人信服的证据表明,
PI-PLC 的全部催化活性需要酶与整个底物(包括疏
水性
脂肪酸链)的相互作用。在这项工作中,我们对
磷脂酰肌醇的结构进行了相对较小的修改,开发出了新的紧密结合且抗裂解的类似物。合成的两种类似物--2-
氨基-2-脱氧-
PI(8)和构象约束类似物(10)的结合亲和力(Ki)在 10 μM 范围内。15N-1H HSQC NMR 光谱显示,15N 标记的细菌 Ca2+ 非依赖性
磷脂酶 C 和 Ca2+ 依赖性
磷脂酶 C(btPLC 和 saPLC1)在与
配体结合后发生了变化,表明发生了构象变化。